1. Technical Field
The present invention relates to a printer that has multiple print head sets for printing on both sides of checks or other recording media, and relates more particularly to a printer having a mechanism that can suitably set the platen gap for each print head assembly.
2. Related Art
A printer having a magnetic head for reading magnetic ink characters printed on checks, and two print head assemblies for printing on the front and back sides of checks is described as a media processing device in Japanese Unexamined Patent Appl. Pub. JP-A-2000-43339 and as a hybrid processing device in Japanese Unexamined Patent Appl. Pub. JP-A-2010-20809.
The front print head and back print head that are used to respectively print on the front and back sides of checks or other recording media are mounted on respective different frame members located on opposite sides of the recording medium transportation path. The platen that defines the printing position of the front print head is mounted on a frame member on the same side as the back print head, and the platen for the back print head is similarly mounted on the frame member on the same side as the front print head.
The platen gap of both print heads is typically narrow at 0.5 mm or less, and precisely disposing the two print heads and platens mounted on different frame members so that such a precise, narrow gap can be achieved is not as simple as when there is only a single print head and platen. More particularly, an external force that displaces both frame members can easily change both platen gaps, and adjusting the platen gaps is more difficult than when there is only one platen gap to be adjusted.
In addition, when the gap between the print head and platen is constant and media of different thicknesses are conveyed, the gap between the print head and the printing surface of the recording medium changes, and problems such as a drop in print quality can result. A problem with the related art is that adjusting the platen gap of both print heads according to the thickness of the recording medium is not possible.